<p> Amphipods are found in large numbers from the top elevation at the Nature Institute (TNI) in Madison County, IL to lower areas of the stream that flow into the Mississippi River. Amphipod success depends greatly on their ability to survive dynamic streams with changing flow and physical conditions. It would be thought that by the end of spring rains, all aquatic organisms would be washed downstream. After observations of persistence of amphipods at the highest reaches of a small fishless stream that experiences relatively severe flooding, the present study sought to determine if a relationship existed between stream elevation and microhabitat type with respect to amphipod abundance. Do certain microhabitats serve as systematically better refuges in flooding streams? This study also sought to determine if there was a relationship between amphipod size and stream elevation. Do larger or smaller amphipods persists better at different stream elevations? Two surveys were conducted in July 2015 with sampling at 8 different elevation zones which included 5 microhabitats. One survey was conducted in August 2015 at 10 different elevation zones (8 of which were repeat areas from July), with samples taken from various elevations along the stream from 5 microhabitats. A total of 2,616 amphipods (Gammarus pseudolimnaeus) were collected over the two-month time period, collected, counted and body length measured. Results did not show a relationship between amphipod body length and stream elevation, nor was there a relationship between amphipod abundance and stream elevation.</p>

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The African indigobirds (Vidua spp.) are exceptional among avian brood parasites in that mimicry of host vocalizations plays an integral role in their social behaviors and evolutionary history. Young indigobirds imprint on the vocalizations of their hosts during development, adult males include mimicry of these vocalizations in their own repertoire, and adult females use these songs to choose both their mates and the nests they parasitize. Imprinting on the host during development therefore results in assortative mating and host fidelity, but also provides a mechanism for rapid, sympatric speciation via host shift. Host shifts require some degree of host infidelity, however, and the same behavioral mechanisms may thus lead to hybridization if eggs are laid in the nest of a host species already "occupied" by another indigobird species. Thus, it is not clear if the morphological and genetic similarity of most indigobird species is due to recent common ancestry or ongoing hybridization. I addressed this uncertainty by studying indigobirds in East Africa, a region that was colonized by West African ancestors in the late Pleistocene and is currently home to four indigobird species. I analyzed variation among species in: vi1) the responses of territorial males to playbacks of conspecific and heterospecific vocalizations; 2) temporal and frequency traits of chatter calls and complex non-mimicry songs; 3) morphological characters; and 4) genomic polymorphisms. The playback experiment shows that host mimicry is an important cue in species recognition, and suggests that it may contribute to species cohesion when juveniles or adults disperse beyond the boundaries of their dialect neighborhood. Analyses of both non-mimetic vocalizations and morphological characters (i.e., plumage color and body size) reveal that they are shaped by divergence among species as well as local ecology. Analyses of thousands of "double-digest" restriction site-associated DNA (ddRAD) loci scattered across the genome indicate that both species identity and geographic divergence contribute to population structure. Taken together, the results show that the tempo of speciation and morphological divergence among indigobirds associated with different hosts is likely variable, depending on geographic context, and the breeding ecology and morphology of alternative hosts.

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